Integrated circuit coolant microchannel assembly with targeted channel configuration

ABSTRACT

A microchannel structure has microchannels formed therein. The microchannels are to transport a coolant and to be proximate to an integrated circuit to transfer heat from the integrated circuit to the coolant. At least one of the microchannels has a length extent and has a first section at a first location along the length extent and a second section at a second location along the length extent. The first section of the microchannel has a first aspect ratio and the second section is divided into at least two sub-channels. Each sub-channel has a respective second aspect ratio that is greater than the first aspect ratio.

BACKGROUND

As microprocessors advance in complexity and operating rate, the heatgenerated in microprocessors during operation increases and the demandson cooling systems for microprocessors also escalate. A particularproblem is presented by so-called “hotspots” at which circuit elementsat a localized zone on the microprocessor die raise the temperature inthe zone above the average temperature on the die. Thus it may not besufficient to keep the average temperature of the die below a targetlevel, as excessive heating at hotspots may result in localized devicemalfunctions even while the overall cooling target is met. This issuemay be applicable to proposed cooling systems in which a coolant such aswater is circulated through narrow channels (known as “microchannels”)which are close to or formed in the die.

Another issue that may be encountered in microchannel cooling systems isthe total pressure drop experienced by the coolant through itscirculation path. The higher the pressure drop, the greater the demandson the pump that circulates the coolant. If higher pumping capacity isrequired, it may be necessary to include a larger and/or more expensiveand/or less reliable pump. Pump size may be especially critical, sincespace may be at a premium, as is the case in notebook computers andother portable computer systems.

Still another issue that may be encountered in microchannel coolingsystems is potential difficulty in connecting tubes for the coolant pathto the potentially delicate cover of a microchannel assembly.

Yet another issue relates to fabricating microchannels that have a highaspect ratio (ratio of height to width). Generally speaking, higheraspect ratios in microchannels provide higher heat transfer rates andlower pressure drops. However, the production processes that may beemployed in accordance with known practices to form high-aspect-ratiomicrochannels may be more expensive than other production processes thatproduce microchannels having smaller aspect ratios.

Another issue is how to reduce pressure drop by shortening the flowlength without changing the geometry of the channels (i.e., to keepparallel flow geometry channels). This may allow for improvedmanufacturability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side cross-sectional view of a system.

FIG. 2 is a schematic view taken in horizontal cross-section of amicrochannel assembly according to some embodiments.

FIG. 3 is a view similar to FIG. 2 of a microchannel assembly accordingto some other embodiments.

FIG. 3A is a view similar to FIGS. 2 and 3 of a microchannel assemblyaccording to other embodiments.

FIG. 4 is a schematic side cross-sectional view of a system according tostill other embodiments.

FIG. 5 is a view similar to FIG. 4 of a system according to otherembodiments.

FIG. 6 is a schematic side cross-sectional view of a microchannelassembly according to further embodiments.

FIG. 7 is a schematic side cross-sectional view showing two members fromwhich a microchannel assembly may be constructed in accordance with someembodiments.

FIG. 8 is a schematic side cross-sectional view showing the microchannelassembly constructed from the members shown in FIG. 7.

FIG. 9 is a schematic side cross-sectional view showing two members fromwhich a microchannel assembly may be constructed in accordance with someother embodiments.

FIG. 10 is a schematic side cross-sectional view showing themicrochannel assembly constructed from the members shown in FIG. 9.

FIG. 11 is a schematic plan view of a microchannel assembly according tostill further embodiments.

FIG. 12 is a schematic vertical sectional view taken along line XII-XIIin FIG. 1.

FIG. 13 is view similar to FIG. 12, showing an alternative embodiment.

FIG. 14 is a schematic vertical sectional view taken along line XIV-XIVin FIG. 11.

FIG. 15 is a block diagram showing a die with additional components of acooling system according to some embodiments.

FIG. 16 is a block diagram of a computer system according to someembodiments that includes an example of an integrated circuit dieassociated with a cooling system as in one or more of FIGS. 2-14.

DETAILED DESCRIPTION

FIG. 1 is a schematic side cross-sectional view of a system 100including an Integrated Circuit (IC) 110. The IC 110 may be associatedwith, for example, an INTEL®PENTIUM IV processor. To help remove heatgenerated by the IC 110, a liquid coolant (not separately shown) may becirculated through a microchannel cold plate 120. The microchannel coldplate 120 may be located proximate to the IC 110 to facilitate theremoval of heat from the system 100. The microchannel cold plate 120may, for example, be thermally coupled to the IC 110 by a thermalinterface material (TIM) 130. (In some cases, the TIM 130 may be omittedand the microchannel cold plate 120 may be directly thermally coupled tothe IC 110. In some cases a rear side of the IC 110 may be thinned toreduce thermal resistance between the IC 110 and the microchannel coldplate 120, which may be coupled to the rear side of the IC 110.) Heatmay be transferred from the IC 110 to the coolant, which may then leavethe system 100. For example, the coolant may exit from the microchannelcold plate 120 via an outlet port 140 and may be circulated to a heatexchanger (not shown) and then to a pump (not shown). The heat exchangermay for example include a length of tube with heat-conductive fins (notshown) mounted thereon and a fan (not shown) to direct air through thefins. Heat transferred to the coolant in the microchannel cold plate 120may be dissipated at the heat exchanger. After passing through the heatexchanger and the pump, the coolant may flow back to the microchannelcold plate 120 via an inlet port 150.

The coolant may be water, or a liquid antifreeze compound that has alower freezing point than water, or an aqueous solution of such acompound.

FIG. 2 is a schematic view taken in horizontal cross-section of amicrochannel assembly 200 according to some embodiments. Themicrochannel assembly 200 may be employed as a microchannel cold platein a system such as that shown in FIG. 1. The microchannel assembly mayhave microchannels 202-1, 202-2, 202-3, 202-4, 202-5 and 202-6 formedtherein, as well as other microchannels which are shown although notassociated with reference numerals. (The number of microchannels in themicrochannel assembly may be more or fewer than the number illustratedin FIG. 2. Also, the drawing is not necessarily to scale. It will beappreciated by those who are skilled in the art that an inlet plenum maybe provided upstream from the microchannels and an outlet plenum may beprovided downstream from the microchannels, in the embodiment of FIG. 2and in other embodiments, although these plenums are not shown, in somecases, so as to simplify the drawings.) The microchannels are defined,in part, by side walls including those indicated by reference numerals204-1, 204-2, 204-3, 204-4 and 204-5. At least some of the side wallsseparate adjacent microchannels from each other. It will be appreciatedthat each microchannel has a length extent which corresponds to adirection in which coolant flows through the microchannel.

The ovals 206, 208 shown in FIG. 2 are indicative of the loci ofhotspots in an IC (not shown in FIG. 2) to which the microchannelassembly 200 may be coupled to cool the IC. In accordance with someembodiments, microchannels located on or near the hotspots may bedivided into sub-channels at the loci of the hotspots. Suchmicrochannels, including for example microchannel 202-6, may have afirst, undivided section 210 at one location along the length extent ofthe microchannel, and a second, divided section 212 at another locationalong the length extent of the microchannel. The divided section 212 mayinclude dividing walls 214 (e.g., three dividing walls in the exampleillustrated, to define four sub-channels) to separate the sub-channelsfrom each other to define the sub-channels along a relatively shortportion of the microchannel at or near the locus of the hotspot. It willbe noted that the dividing walls are oriented parallel to the lengthextent of the microchannels in which they are provided. The dividingwalls may extend normal to the floor (not shown) of the microchannels.

The microchannels exhibit a first aspect ratio in their undividedportions. The aspect ratio is defined as the ratio of height to width,where the height is the vertical dimension and the width is thehorizontal dimension that is transverse to the direction of coolantflow. (As a matter of convention the vertical direction will be taken tobe the direction from the microchannel assembly to the IC die which itcools.) It will be understood that the sub-channels share the sameheight as the undivided portions of the microchannels, but have a muchnarrower width, and therefore the sub-channels have a much greateraspect ratio than the undivided portions of the microchannels. Becauseof the greater aspect ratios of the sub-channels, the divided portionsof the microchannels provide substantially greater heat transfercapability than the undivided portions, thereby providing targetedimprovements in cooling ability at the hotspots. There may be anincreased pressure drop at the divided portions of the microchannels,but since the divided portions run for only a relatively short distancealong the microchannels, the total pressure drop caused by the dividingof the microchannels may be rather small, so that the targeted dividingof the microchannels may lead to an improved trade-off between heattransfer capability and pressure drop. The use of targeted division ofthe microchannels may satisfy cooling requirements while allowing use ofa relatively reliable centrifugal pump rather than a higher capacity butless reliable positive displacement pump. As an alternative to either ofthese types of pump, an electrokinetic pump may be employed. With anytype of pump, the relatively small pressure drop associated with thetargeted division of microchannels may allow for savings in terms of thepower requirements for the pump and/or the size and capacity of thepump.

The number of sub-channels into which a microchannel is divided may bemore or fewer than the four sub-channels shown in the exemplaryembodiment of FIG. 2, and the number of sub-channels may vary frommicrochannel to microchannel. The microchannels need not be straight.Exemplary dimensions of the microchannels (in the undivided sections)may be 150 microns wide by 300 microns high, although these dimensionsmay be varied as appropriate. The microchannels may be formed in aconventional material, such as silicon or copper, and by a conventionalprocess, such as dry etching. Although not shown in the drawings, themicrochannel assembly 200 may also include, in accordance withconventional practices, an inlet reservoir or manifold at one end of themicrochannels and an outlet reservoir or manifold at the other end ofthe microchannels.

FIG. 3 is a view similar to FIG. 2 of a microchannel assembly 300according to some other embodiments. The microchannel assembly 300 maybe the same as the microchannel assembly 200 of FIG. 2, except that atleast some of the microchannels (e.g., microchannels 302-1, 302-2) whichare not subdivided and do not pass over hotspots may have a narrowerwidth than the width exhibited at undivided portions of themicrochannels (e.g., 304-1, 304-2) that pass over and are subdivided athotspots. The provision of narrow channels that do not cool hotspots mayhelp to balance the pressure drop among all microchannels and to allowfor adequate coolant flow into the divided microchannels that coolhotspots. As in the prior example, the wider microchannels may, in theirundivided sections, be 150 microns wide by 300 microns high, and thenarrower microchannels may be 50 microns wide by 300 microns high.Again, the dimensions may be varied as appropriate.

FIG. 3A is a view similar to FIGS. 2 and 3 of a microchannel assembly320 according to other embodiments. The microchannel assembly hasrelatively wide or sparse microchannels 322-1, 322-2, 322-3 at the locusof a cache area (indicated by dashed-line rectangle 324 and being aportion of a microprocessor which generally is not shown), whichrequires a relatively small cooling efficiency. The microchannels 322are divided into relatively narrow or dense sub-channels 326 at thelocus of a core area (indicated by dashed-line rectangle 328), which isa part of the microprocessor that requires a greater cooling efficiency.In the particular example shown in FIG. 3A, each microchannel 322 isdivided into five sub-channels 326 at the core area 328. It will beappreciated that the sub-channels 326 have a greater aspect ratio thanthe undivided portions of the microchannels 322. (The number ofmicrochannels and/or the number of sub-channels may be more or fewerthan the number illustrated in FIG. 3A, and the drawing is notnecessarily to scale.)

Coolant (not shown) flows to the sub-channels 326 via an inlet 330 andan inlet plenum 332. The coolant flows out of the microchannels 322 viaan outlet plenum 334 and an outlet 336. (It will be appreciated that thedirection of coolant flow may be reversed in some embodiments.)

FIG. 4 is a schematic side cross-sectional view of a system 400according to still other embodiments. The system 400 includes an IC 402(e.g. a microprocessor or “CPU” die) and a microchannel assembly 404thermally coupled to the IC 402 by a TIM 406. The microchannel assembly404 includes a microchannel structure 408 which has microchannels (notshown in detail) formed therein. In particular, the microchannelstructure 408 may define bottom and side walls of microchannels in whichcoolant is to be transported in proximity to the IC 402 for heat to betransferred to the coolant from the IC 402. The microchannel structure408 may be provided in accordance with conventional practices or may beconfigured as in one of the microchannel assemblies illustrated in FIGS.2 and 3. Other variations in the microchannel layout are possible.

The microchannel assembly 404 also includes a cover plate 410 positionedon (e.g., bonded to) the microchannel structure 408 to define top wallsof the microchannels. The cover plate 410 may be provided in accordancewith conventional practices and may have formed therein an inlet port412 and an outlet port 414. The inlet port 412 is to allow coolant toflow into the microchannel structure 408 and the outlet port 414 is toallow coolant to flow out of the microchannel structure 408.

In addition, the microchannel assembly 404 includes a manifold plate 416that is mounted on the cover plate 410 to facilitate connection to themicrochannel assembly of tubing (not shown) for the coolant. Themanifold plate 416 may, for example, be adhered to the top surface ofthe cover plate 410 by solder or by a sealant 418 such as epoxy orsilicone. The manifold plate 416 has a lower horizontal surface 420, aleft side vertical surface 422 and a right side vertical surface 424.(As used herein and in the appended claims, a “vertical surface” shouldbe understood to include any surface that departs substantially from thehorizontal; and “horizontal” refers to any direction normal to thedirection from the microchannel assembly to the IC.)

The manifold plate 416 has formed therein an inlet passage 426. Theinlet passage 426 provides fluid communication between a port 428 on thelower horizontal surface 420 of the manifold plate 416 and a port 430 onthe left side vertical surface 422. The inlet passage 426 is aright-angle passage in that it is formed of a vertical course 432 and ahorizontal course 434 that joins the vertical course 436 at a rightangle. (More generally, as used herein and in the appended claims,“right-angle passage” refers to any passage that supports at least an85° change in flow direction therethrough.) The manifold plate 416 isadhered to the cover plate 410 in such a manner that the port 428 of themanifold plate 416 is aligned with the inlet port 412 of the cover plate410. Advantageously, the sealant 418 (or alternatively solder, as thecase may be) is deployed in such a manner that coolant flows from theport 428 to the inlet port 412 without leakage.

The manifold plate 416 also has formed therein an outlet passage 436.The outlet passage 436 provides fluid communication between a port 438on the lower horizontal surface 420 of the manifold plate 416 and a port440 on the right side vertical surface 424. The outlet passage 436 is aright-angle passage in that it is formed of a vertical course 442 and ahorizontal course 444 that joins the vertical course at a right angle.The port 438 of the manifold plate 416 is aligned with the outlet port414 of the cover plate 410. Sealant 418 (or solder, as the case may be)may be deployed in such amanner that coolant flows from the outlet port414 to the port 438 without leakage.

A clamp (not shown) or the like may apply a downward force to the uppersurface 446 of the manifold plate 416 to retain the manifold plate 416in position on the cover plate 410.

The manifold plate 416 may be formed of a suitable material such ascopper, ceramic or polymer. Each passage 426, 436 may be formed with twodrilling operations—one from the horizontal surface 420 and one from thevertical surface 422 or 424 as the case may be. It is not critical as tothe order in which the two drilling operations are performed for a givenone of the passages 426, 436. In some embodiments a molding process mayperformed as an alternative to drilling. For example, the manifold platemay have suitable fittings incorporated therein and may be formed bymolding around metal tubes that constitute the right angle passages andthe fittings.

The presence of the manifold plate 416 as part of the microchannelassembly 404 may facilitate connection of tubing (for coolantcirculation) to the microchannel assembly 404. A tube (not shown)leading from the heat exchanger and the pump (both not shown) may beconnected at the port 430 of the inlet passage 426 of the manifold plate416.

Another tube (not shown) leading to the heat exchanger and the pump maybe connected at the port 440 of the outlet passage 436 of the manifoldplate 416. The manifold plate 416 may be more robust than a typicalcover plate for a micro channel assembly and may reduce the possibilityof breakage of the cover plate, and may help to insure reliable tubeconnection. In general, the presence of the manifold plate mayfacilitate high volume manufacturing (HVM) with regard to the system.

Moreover, the horizontal-facing ports 430, 440 of the passages 426, 436,respectively, may allow for improvements in form factor for the coolingsystem as a whole. Also, if it is desired to modify the configuration ofthe tubing and/or manner of connection of tubing to the microchannelassembly, such a modification may be accommodated by a manifold platehaving a different configuration, without requiring modification of thecover plate. In other words, the manifold plate may be tailored to matchthe desired orientation of inlet/outlet tubes, while keeping the coverplate and microchannel structure unchanged.

FIG. 5 is a view similar to FIG. 4 of a system 500 according to otherembodiments. The system 500 may include all of the constituent parts ofthe system 400 (FIG. 4) as described above, but in the system 500 themanifold plate 416 is integrated with the package 502 for the IC 402. Inparticular, the manifold plate may form the upper wall of the package502, which may also be formed of (a) side walls 504, 506 joined to themanifold plate 416 at respective ends of the manifold plate 416, and (b)a package substrate 508 on which the IC 402 is mounted, and which isjoined to the lower ends of the side walls 504, 506.

In the system 500, with the microchannel assembly effectively integratedwith the IC package, it may not be necessary to apply an externalretaining force to keep the manifold plate 416 in place on the coverplate 410.

FIG. 6 is a schematic side cross-sectional view of a microchannelassembly 600 according to further embodiments. The microchannel assembly600 may include a microchannel structure 602 which is like themicrochannel structure 408 described above in connection with FIG. 4. Inaddition, the microchannel assembly 600 may include a cover plate 604positioned on the microchannel structure 600. The cover plate 604 may beformed in similar manner to the manifold plate 416 described above inconnection with FIG. 4. In particular, the cover plate 604 may haveformed therein two right-angle passages 606, 608 like the inlet passage426 and the outlet passage 436 described above in connection with FIG.4. Thus, in this microchannel assembly 600, the cover plate and manifoldplate of previously described embodiments may effectively be integratedtogether to form a plate which defines upper walls of the microchannelswhile facilitating connection of tubing to the microchannel assembly.

In the manifold plate 416 and cover plate 604 illustrated above, thehorizontal course of the outlet passage is formed at the oppositevertical surface from the horizontal course of the inlet passage.However, in alternative embodiments, the horizontal courses of both theinlet passage and the outlet passage may be formed at the same surfaceor at respective vertical surfaces that are oriented 900 apart from eachother (i.e., at adjoining vertical surfaces).

FIG. 7 is a schematic side cross-sectional view showing two members 702,704 from which a microchannel assembly may be constructed in accordancewith some embodiments. FIG. 8 is a schematic side cross-sectional viewshowing the resulting microchannel assembly 802 constructed from themembers 702, 704. In both drawings, the cross-section is takentransversely to the direction of flow of the coolant. Each of themembers 702, 704 may be generally in the form of a conventionalmicrochannel structure (which would be covered by a flat lid ifconventional practice were to prevail). Alternatively, varyingmicrochannel widths and/or subdividing of microchannels at hotspots, asdescribed above, may be implemented in the members 702, 704. The members702, 704 may be identical to each other in over-all form, except, e.g.,for features such as inlet/outlet holes (not shown) in one of themembers 702, 704. Thus each member may have a base 706 and parallelwalls 708 each extending normally from the base 706. The walls 708 arefor defining side walls of the microchannels 804 (FIG. 8) in theresulting microchannel assembly 802. Each of the walls 708 has arespective outer end 710.

In assembling the microchannel assembly 802 from the members 702, 704,the members 702, 704 may be bonded to each other by bonding therespective outer end 710 of each of the parallel walls 708 of the member702 to the respective outer end 710 of a respective parallel wall 708 ofthe member 704 in a mirror-image configuration as shown in FIG. 8. Inthis arrangement, the walls 708 of member 702 cooperate with walls 708of member 704 to define the side walls of the microchannels 804. Inparticular, in this arrangement, the walls 708 of member 702 providehalf the height of the microchannels 804 while the walls 708 of member704 provide the other half of the height of the microchannels 804.

Each of the members 702, 704 may be made of a conventional material fora microchannel structure and the gaps between the parallel walls may beformed by a conventional and relatively inexpensive process such as dryetching to provide gaps having an aspect ratio of about five, forexample. It will be appreciated that the microchannels in the resultingmicrochannel assembly 802 have twice the aspect ratio (ten in thisexample) of the gaps. In this way, an advantageous process may beemployed to form high aspect ratio microchannels even though the processif employed in a conventional manner could only produce lower aspectratio microchannels. With the higher aspect ratio for the microchannels,the pressure drop for the coolant flow through the microchannels may bereduced, thereby in turn reducing the requirements for the pump employedin the cooling system. Also, the increased aspect ratio may promote animproved heat transfer rate and thus more effective cooling.

Each of the members 702, 704 may, in some embodiments, be formed as aunitary body. The bonding of one member to another may be by diffusionbonding, eutectic bonding or other suitable process.

FIG. 9 is a schematic side cross-sectional view showing two members 902,904 from which a microchannel assembly may be constructed in accordancewith some other embodiments. FIG. 10 is a schematic side cross-sectionalview showing the resulting microchannel assembly 1002 constructed fromthe members 902, 904. In both drawings, the cross-section is takentransversely to the direction of flow of the coolant.

Member 902 may be generally in the form of a conventional microchannelstructure (to be covered by a flat lid if conventional practice were toprevail), but possibly with deeper and wider gaps formed betweenparallel walls 906, which extend normally from base 908 of member 902.Each wall 906 has a respective outer end 910.

Member 904 may be similar to member 902, and may have a base 912 andparallel walls 914 which extend normally from base 912. Member 904 maydiffer from member 902 in that the outermost ones of the walls 914 mayboth be recessed from a respective end of the base 912. In otherembodiments, however, the members 904, 902 may be substantiallyidentical, except possibly for the presence of inlet and outlet holes inone of the members. Each wall 914 has a respective outer end 916.

In assembling the microchannel assembly 1002 from members 902, 904, thewalls 906 of member 902 may be interleaved with the walls 914 of member904 and the outer ends 910 of walls 906 of member 902 may be bonded tothe base 912 of the member 904, and the outer ends 916 of walls 914 ofmember 904 may be bonded to the base 908 of the member 902. In thisarrangement, the walls 906 of member 902 cooperate with the walls 914 ofthe member 904 to define microchannels 1004 (FIG. 10) in themicrochannel assembly 1002. In particular, in each microchannel, oneside wall is defined by a wall 906 of member 902 and the other side wallis defined by a wall 914 of member 904.

Each of the members 902, 904 may be made of a conventional material fora microchannel structure and the gaps between parallel walls may beformed by a conventional and relatively inexpensive process such as dryetching to provide gaps having an aspect ratio of five, for example. Itwill be appreciated that the microchannels in the resulting microchannelassembly 1002 have an aspect ratio that is more than twice the aspectratio of the gaps in the individual members. In this way, anadvantageous process may be employed to form high aspect ratiomicrochannels even though the process if employed in a conventionalmanner could only produce a lower aspect ratio microchannel. With thehigher aspect ratio, lower pressure drops and/or improved heat transfermay be achieved.

Each of the members 902, 904 may, in some embodiments, be formed as aunitary body. The bonding of one member to another may be by diffusionbonding, eutectic bonding or other suitable process.

FIG. 11 is a schematic plan view of a microchannel assembly 1102according to still further embodiments. FIG. 12 is a schematic verticalsectional view of the microchannel assembly 1102 taken along lineXII-XII in FIG. 11. FIG. 14 is a schematic vertical sectional view ofthe microchannel assembly 1102 taken along line XIV-XIV in FIG. 11.

The microchannel assembly 1102 includes a microchannel structure 1402(FIG. 14) which has microchannels 1404 formed therein. The microchannels1404, as in previous embodiments, are for transporting a coolant and areto be located proximate to an integrated circuit (not shown in FIGS. 11,12, 14) to transfer heat from the IC to the coolant. The microchannelstructure 1402 may be provided in accordance with conventional practicesor alternatively may be configured as described in connection with FIGS.2 and 3.

The microchannel assembly 1102 also includes a lid 1406 (FIG. 14) whichis positioned on the microchannel structure 1402 to define the upperwalls of the microchannels 1404. As best seen in FIG. 11, the lid 1406has formed therein an inlet 1104 and an inlet 1106. The inlets 1104,1106 are located at respective opposite ends of the microchannelassembly 1102 and hence are formed at respective opposite ends of thelid 1406. The inlets are to allow coolant to flow into the microchannelassembly 1102.

The lid 1406 also has a plenum 1108 (FIGS. 11, 12, 14) formed therein.As indicated in FIG. 14, the plenum 1108 extends across and above themicrochannels 1404 at a central location of the microchannels. Morespecifically, and as seen from FIG. 11, the longitudinal axis of theplenum 1108 is perpendicular to a line (not shown) drawn from one inlet1104 to the other inlet 1106 and is substantially equidistant from, andpositioned between, the inlets 1104, 1106. It will be noted that theplenum 1108 is centrally located relative to the microchannel assembly.At a central location along the plenum 1108, an outlet 1110 is formed toallow coolant to flow out of the microchannel assembly 1102. In someembodiments, a manifold (not shown) may be positioned on the lid 1406 tomanage distribution of coolant between the inlets 1104, 1106 and to takecoolant out from the outlet 1110.

The lid may, for example, be formed of copper and the plenum may beformed by a stamping operation.

In operation, coolant is flowed into the microchannel assembly 1102 viathe inlets 1104, 1106. The coolant flows from the inlets into oppositeends of the microchannels via reservoirs 1112 (indicated in phantom inFIG. 11). The coolant flows from the opposite ends of each microchannelto a central location of the respective microchannel, as indicated inFIG. 12. From the central location in the microchannel, the coolantflows up into the plenum 1108. In the case of each microchannel notlocated directly under the outlet 1110, the coolant from the respectivemicrochannel flows through the plenum toward the outlet 1110 (i.e.,toward the center of the lid 1406). The coolant then flows out of themicrochannel assembly via the outlet 1110.

With this arrangement of flowing coolant from both ends of eachmicrochannel toward a central location along the microchannel, the pathof coolant flow along the microchannel from inlet to outlet is reducedby one-half relative to a given over-all length of the microchannel. Asa result, the pressure drop along the coolant path from inlet to outletmay be substantially reduced (e.g., by about half), thereby reducing therequirements for the pump needed in the cooling system.

Instead of flowing the coolant from the ends of the microchannels towardthe center of the microchannel assembly, in other embodiments thecoolant may flow from the center of the microchannel assembly out towardboth ends of the microchannels, as schematically illustrated in FIG. 13.In this case essentially the same structure may be used, but the centralport is used as an inlet (labeled 1302 in FIG. 13), and the ports at theends of the microchannel are used as dual outlets (labeled 1304, 1306 inFIG. 13).

The various embodiments described above may be combined in a variety ofways. For example, the manifold plate (FIGS. 4, 5) or integratedmanifold/lid (FIG. 6) may be used in conjunction with the microchannelstructures of FIGS. 2, 3 or 8, 10 and/or with the reduced flow lengthinlet/outlet arrangements of FIGS. 11-14. For example, a manifold plateor lid may provide right-angle passages for each of the inlets/outletsshown in the embodiments or FIGS. 11-14. Other combinations of featuresdisclosed herein may also be implemented.

FIG. 15 is a block diagram showing an IC die 1510 and additionalcomponents of a cooling system 1500. For purposes of illustration themicrochannel assembly 1540 (which may be any one of the microchannelassemblies described above) is shown as a single block. The coolingsystem 1500 includes a coolant circulation system 1590 to supply thecoolant to the microchannel assembly 1540. The coolant circulationsystem 1590 may be in fluid communication with the microchannel assembly1540 via one or more coolant supply channels or lines 1592 and one ormore coolant return channels 1594. Although not separately shown, a pumpand a heat exchanger located remotely from the die 1510 may be includedin the coolant circulation system 1590.

Coolant supplied by the coolant circulation system 1590 may flow throughthe microchannels of the microchannel assembly 1540 at or above the rearsurface of the IC die 1510 to aid in cooling the IC die 1510. In someembodiments, the coolant is operated with two phases—liquid and vapor.That is, in some embodiments at least part of the coolant in themicrochannels is in a gaseous state. In other embodiments, the coolantis single phase—that is, all liquid.

The IC die 1510 may be associated with a microprocessor in someembodiments. FIG. 16 is a block diagram of a system 1600 in which such adie 1610 may be incorporated. In particular, the die 1610 includes manysub-blocks, such as an Arithmetic Logic Unit (ALU) 1604 and an on-diecache 1606. The microprocessor on die 1610 may also communicate to otherlevels of cache, such as off-die cache 1608. Higher memory hierarchylevels, such as system memory 1611, may be accessed via a host bus 1612and a chipset 1614. In addition, other off-die functional units, such asa graphics accelerator 1616 and a Network Interface Controller (NIC)1618, to name just a few, may communicate with the microprocessor on die1610 via appropriate busses or ports.

The IC die 1610 may be cooled in accordance with any of the embodimentsdescribed herein. For example, a pump 1690 may circulate a coolant(e.g., including water) through a cold plate 1640 proximate to the ICdie 1610 and having at least one microchannel to transport the coolant.

The system architecture shown in FIG. 16 is exemplary; other systemarchitectures may be employed.

The several embodiments described herein are solely for the purpose ofillustration. The various features described herein need not all be usedtogether, and any one or more of those features may be incorporated in asingle embodiment. Therefore, persons skilled in the art will recognizefrom this description that other embodiments may be practiced withvarious modifications and alterations.

1-7. (canceled)
 8. An apparatus comprising: a microchannel structurehaving microchannels formed therein, said microchannels to transport acoolant and to be proximate to an integrated circuit to transfer heatfrom the integrated circuit to the coolant; a cover positioned on themicrochannel structure; and a plate mounted on said cover, said platehaving formed therein a right-angle passage to provide fluidcommunication between a first port on a lower horizontal surface of saidplate and a second port on a vertical surface of said plate.
 9. Theapparatus of claim 8, wherein said first port is aligned with an inletformed in said cover.
 10. The apparatus of claim 9, wherein saidright-angle passage is a first right-angle passage; said plate alsohaving formed therein a second right-angle passage to provide fluidcommunication between a third port on said lower horizontal surface ofsaid plate and a fourth port on a vertical surface of said plate;wherein said third port is aligned with an outlet formed in said cover.11. An apparatus comprising: a microchannel structure havingmicrochannels formed therein, said microchannels to transport a coolantand to be proximate to an integrated circuit to transfer heat from theintegrated circuit to the coolant; a cover positioned on themicrochannel structure and having formed therein a right-angle passageto provide fluid communication between a first port on a lowerhorizontal surface of said cover and a second port on a vertical surfaceof said cover.
 12. The apparatus of claim 11, wherein said right-anglepassage is a first right-angle passage; said cover also having formedtherein a second right-angle passage to provide fluid communicationbetween a third port on said lower horizontal surface of said cover anda fourth port on said vertical surface of said cover.
 13. The apparatusof claim 11, wherein said right-angle passage is a first right-anglepassage and said vertical surface is a first vertical surface; saidcover also having formed therein a second right-angle passage to providefluid communication between a third port on said lower horizontalsurface of said cover and a fourth port on a second vertical surface ofsaid cover, said second vertical surface being different from said firstvertical surface.
 14. A microchannel assembly comprising: a first memberhaving a base and parallel walls extending normally from said base; anda second member having a base and parallel walls extending normally fromsaid base of said second member; said second member bonded to said firstmember such that said parallel walls of said second member cooperatewith said parallel walls of said first member to define microchannels,said microchannels to transport a coolant and to be proximate to anintegrated circuit to transfer heat from the integrated circuit to thecoolant.
 15. The microchannel assembly of claim 14, wherein: each ofsaid parallel walls of said first member has a respective outer end;each of said parallel walls of said second member has a respective outerend; and the respective outer end of each of said parallel walls of saidfirst member is bonded to the respective outer end of a respective oneof said parallel walls of said second member.
 16. The microchannelassembly of claim 14, wherein: each of said parallel walls of said firstmember has a respective outer end; each of said parallel walls of saidsecond member has a respective outer end; the outer ends of the parallelwalls of said first member are bonded to said base of said secondmember; and the outer ends of the parallel walls of said second memberare bonded to said base of said first member.
 17. A method comprising:providing a first member having a base and parallel walls extendingnormally from said base; providing a second member having a base andparallel walls extending normally from said base of said second member;and bonding said first member to said second member to form amicrochannel assembly.
 18. The method of claim 17, wherein: each of saidparallel walls of said first member has a respective outer end; each ofsaid parallel walls of said second member has a respective outer end;and said bonding includes bonding the respective outer end of each ofsaid parallel walls of said first member to the respective outer end ofa respective one of said parallel walls of said second member.
 19. Themethod of claim 18, wherein: each of said parallel walls of said firstmember has a respective outer end; each of said parallel walls of saidsecond member has a respective outer end; and said bonding includes:bonding the respective outer end of each of said parallel walls of saidfirst member to the base of said second member; and bonding therespective outer end of each of said parallel walls of said secondmember to the base of said first member.
 20. A method comprising:supplying a microchannel assembly having at least one microchannelformed therein, said at least one microchannel to transport a coolantand to be proximate to an integrated circuit to transfer heat from theintegrated circuit to the coolant; and flowing a coolant from oppositeends of said at least one microchannel to a central location of said atleast one microchannel.
 21. The method of claim 20, wherein the coolantis flowed into said microchannel assembly via two inlets, including afirst inlet located at a first end of the microchannel assembly and asecond inlet located at a second end of the microchannel assembly, saidsecond end opposite said first end.
 22. The method of claim 21, whereinthe coolant is flowed out of said microchannel assembly via a plenumthat is centrally located relative to said microchannel assembly.
 23. Amethod comprising: supplying a microchannel assembly having at least onemicrochannel formed therein, said at least one microchannel to transporta coolant and to be proximate to an integrated circuit to transfer heatfrom the integrated circuit to the coolant; and flowing a coolant from acentral location of said at least one microchannel to opposite ends ofsaid at least one microchannel.
 24. The method of claim 23, wherein thecoolant is flowed out of said microchannel assembly via two outlets,including a first outlet located at a first end of the microchannelassembly and a second outlet located at a second end of the microchannelassembly, said second end opposite said first end.
 25. The method ofclaim 24, wherein the coolant is flowed into said microchannel assemblyvia a plenum that is centrally located relative to said microchannelassembly.
 26. A microchannel assembly having microchannels formedtherein, said microchannels to transport a coolant and to be proximateto an integrated circuit to transfer heat from the integrated circuit tothe coolant, said microchannel assembly having two inlets to allowcoolant to flow into said microchannel assembly, said two inletsincluding a first inlet located at a first end of said microchannelassembly and a second inlet located at a second end of said microchannelassembly, said second end opposite said first end, said microchannelassembly also having an outlet to allow coolant to flow out of saidmicrochannel assembly.
 27. The microchannel assembly of claim 26,wherein said outlet is between and substantially equidistant from saidinlets.
 28. The microchannel assembly of claim 27, further comprising aplenum which extends across and above said microchannels at a centrallocation of said microchannels to allow coolant to flow from saidmicrochannels to said outlet.
 29. The microchannel assembly of claim 27,wherein said microchannels are formed in a microchannel structure, saidassembly further comprising: a cover positioned on the microchannelstructure, said cover having at least one right-angle passage formedtherein to allow fluid to flow to one of said inlets or from saidoutlet.
 30. A microchannel assembly having microchannels formed therein,said microchannels to transport a coolant and to be proximate to anintegrated circuit to transfer heat from the integrated circuit to thecoolant, said microchannel assembly having two outlets to allow coolantto flow out of said microchannel assembly, said two outlets including afirst outlet located at a first end of said microchannel assembly and asecond outlet located at a second end of said microchannel assembly,said second end opposite said first end, said microchannel assembly alsohaving an inlet to allow coolant to flow into said microchannelassembly.
 31. The microchannel assembly of claim 30, wherein said inletis between and substantially equidistant from said outlets.
 32. Themicrochannel assembly of claim 31, further comprising a plenum whichextends across and above said microchannels at a central location ofsaid microchannels to allow coolant to flow from said inlet to saidmicrochannels.
 33. The microchannel assembly of claim 30, wherein saidmicrochannels are formed in a microchannel structure, said assemblyfurther comprising: a cover positioned on the microchannel structure,said cover having at least one right-angle passage formed therein toallow fluid to flow from one of said outlets or to said inlet.